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I have a Yanmar 30GM3F that is spitting the dipstick out like a rocket.  I obviously have some unwanted compression in the oil pan.  Its about 30 years old so it wouldn't surprise me if it needs new rings but I thought I would run it by anyone who wants to help me diagnose the issue.  Here is what happened so far.

 

1) it was very difficult to start so we bleed all the lines repeatedly and eventually got it started but then after a few minutes it blew the dipstick;

2) I read somewhere that a blocked breather could cause unwanted pressure in the oil so I pulled the hose off the breather and saw that smoky air was blowing out pretty freely so I decided it probably wasn't blocked...but I'm not sure if "smoky air" should even be blowing out of the breather.

3) We checked the oil and saw that it was unusually high.  We could have overfilled it but I assumed that the lift pump diaphragm might have been busted and slowly leaking diesel into the oil eventually raising its level so we changed the oil and replaced the lift pump.  (after bleeding it forever, again, we got it started started and then it blew out the dipstick again)

4) At this point I'm pretty sure I'm getting compression in the oil so I narrowed the problem to these guesses:

         1) bad rings;

         2) a weird head gasket failure that isn't introducing water to the oil but somehow is introducing compression to the oil through one of the holes in the block (not sure if that is even           

              possible); or

         3) a hole in a piston.

My next action is to check the compression in each cylinder to get that data point before tearing it apart.

Any thoughts? Suggestions?

 

 

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you can get a test kit that samples air / gasses being pushed out through your coolant to see if it contains combustion gasses. Might help to chase down the problem.

When it blows out the dipstick does it shoot out a jet of hot oil with it?

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1 hour ago, Tharsheblows said:

I have a Yanmar 30GM3F that is spitting the dipstick out like a rocket.  I obviously have some unwanted compression in the oil pan.  Its about 30 years old so it wouldn't surprise me if it needs new rings but I thought I would run it by anyone who wants to help me diagnose the issue.  Here is what happened so far.

 

1) it was very difficult to start so we bleed all the lines repeatedly and eventually got it started but then after a few minutes it blew the dipstick;

2) I read somewhere that a blocked breather could cause unwanted pressure in the oil so I pulled the hose off the breather and saw that smoky air was blowing out pretty freely so I decided it probably wasn't blocked...but I'm not sure if "smoky air" should even be blowing out of the breather.

3) We checked the oil and saw that it was unusually high.  We could have overfilled it but I assumed that the lift pump diaphragm might have been busted and slowly leaking diesel into the oil eventually raising its level so we changed the oil and replaced the lift pump.  (after bleeding it forever, again, we got it started started and then it blew out the dipstick again)

4) At this point I'm pretty sure I'm getting compression in the oil so I narrowed the problem to these guesses:

         1) bad rings;

         2) a weird head gasket failure that isn't introducing water to the oil but somehow is introducing compression to the oil through one of the holes in the block (not sure if that is even           

              possible); or

         3) a hole in a piston.

My next action is to check the compression in each cylinder to get that data point before tearing it apart.

Any thoughts? Suggestions?

 

 

Don’t know your engine but it’s common to have a crankcase breather 

the breather is a steel wool filter insidec a canister 

over time this canister , breather , gets clogged and must be washed out with solvent 

the white painted canister , aft of the fuel filters in the picture 

6BADAC61-E1D5-457F-8611-CA58227E851D.png

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5 minutes ago, blunted said:

you can get a test kit that samples air / gasses being pushed out through your coolant to see if it contains combustion gasses. Might help to chase down the problem.

When it blows out the dipstick does it shoot out a jet of hot oil with it?

When the dipstick blew it rocketed out with a trail of oil...and bounced off the wall of the wall.

Regarding the test kit, are talking about testing the exhaust to see if the rings air failing?  Or testing the coolant fluid for combustion gases.  As far as I know the coolant system is working (no overheating and the oil doesn't look like it is getting mixed with coolant)

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I thought you could use the kit that tests the gasses on the dipstick tube to see if exhaust gases are being expelled through there. Then you would know where it's coming from. It's a start.

One would assume that the dipstick comes from the bottom of the sump so gases trapped in the pan must push that oil down and out of that tube in a large supply until the oil ends up below the level of the tube and gasses can pass freely. Air locked so to speak.

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6 minutes ago, slug zitski said:

Don’t know your engine but it’s common to have a crankcase breather 

the breather is a steel wool filter insidec a canister 

over time this canister , breather , gets clogged and must be washed out with solvent 

the white painted canister , aft of the fuel filters in the picture 

6BADAC61-E1D5-457F-8611-CA58227E851D.png

Yes, it has a breather.  the breather is on the valve cover and sends a small tube to the air intake (to reburn fumes I assume).  I pulled the tube off and saw a steady stream of white smoky air blowing out.  I assumed the steel wool like filter in the breather box was ok because smoky air was flowing out so well and the tube wasn't clogged.  But i never cracked open and cleaned the breather and it looked like some oil had gone down the tube and hit the air filter so the whole mechanism may still need some cleaning.

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7 minutes ago, blunted said:

I thought you could use the kit that tests the gasses on the dipstick tube to see if exhaust gases are being expelled through there. Then you would know where it's coming from. It's a start.

One would assume that the dipstick comes from the bottom of the sump so gases trapped in the pan must push that oil down and out of that tube in a large supply until the oil ends up below the level of the tube and gasses can pass freely. Air locked so to speak.

I think combustion blow-by would certainly pressurize the oil and blow the dipstick out.  The fact that the engine has a breather means (I assume) some blow by is expected and normal? no?

Does anyone know the classic signs of failing rings?  I'm guessing failure to start immediately might be a sign (low compression).

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The crankcase is supposed to communicate with the head via a vent line to allow blow-by to vent up and out of the valve cover. If that communication is blocked, you'll pressurize the crankcase and that can lead to a dipstick launch. I'd look for a blockage like that before going all medieval on the engine.

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A good engine will have a barely noticeable flow from the breather tube. Your description is extreme. Does the engine run smooth*? Start easy (after the bleeding you described)? Really? Sounds like at hole in a piston or completely failed rings. A rising oil level can be caused by the fuel in a non-firing piston getting past the piston into the sump. 

That’s a 3 cylinder, right? So one dead cylinder should cause an odd Harley-Davidson irregular pulse. Should be obvious.  
 

Remove and replace using a VISA card...

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3 minutes ago, IStream said:

The crankcase is supposed to communicate with the head via a vent line to allow blow-by to vent up and out of the valve cover. If that communication is blocked, you'll pressurize the crankcase and that can lead to a dipstick launch. I'd look for a blockage like that before going all medieval on the engine.

Thank you!  That is one more potential less than fatal problem I can look at before accepting my likely fate

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13 minutes ago, IStream said:

The crankcase is supposed to communicate with the head via a vent line to allow blow-by to vent up and out of the valve cover. If that communication is blocked, you'll pressurize the crankcase and that can lead to a dipstick launch. I'd look for a blockage like that before going all medieval on the engine.

The passages between the crankcase and valve cover are numerous and large, no? At least one per pushrod, or a few oil return passages...I would think.

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49 minutes ago, Tharsheblows said:

Yes, it has a breather.  the breather is on the valve cover and sends a small tube to the air intake (to reburn fumes I assume).  I pulled the tube off and saw a steady stream of white smoky air blowing out.  I assumed the steel wool like filter in the breather box was ok because smoky air was flowing out so well and the tube wasn't clogged.  But i never cracked open and cleaned the breather and it looked like some oil had gone down the tube and hit the air filter so the whole mechanism may still need some cleaning.

Pull the injectors and inspect the color for unburnt fuel 

do a compression test 

 

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4 minutes ago, El Borracho said:

A good engine will have a barely noticeable flow from the breather tube. Your description is extreme. Does the engine run smooth*? Start easy (after the bleeding you described)? Really? Sounds like at hole in a piston or completely failed rings. A rising oil level can be caused by the fuel in a non-firing piston getting past the piston into the sump. 

That’s a 3 cylinder, right? So one dead cylinder should cause an odd Harley-Davidson irregular pulse. Should be obvious.  
 

Remove and replace using a VISA card...

Unfortunately, I think you are right. 

A little more backstory, the incident happened when we were pulling out of the slip to go race and the engine sneezed and died (it had never done that before).  We looked and saw oil all over the top of the engine.  Because we were late to the race we ended up just sailing out to race and sailing back to the slip.

When we got around to fixing the engine I tackled many obvious issues first like snot in the racor, etc... so I wasn't surprised that I had to bleed it.  It had previously usually started up on the first try but it always sounded like jackhammer to the side of your head at idle so its hard so say if it sounded bad.

Now I think the oil we saw burst out of the breather tube...which shouldn't have oil in it except the oil level was very high and the pressure was very high.  We could have been leaking diesel from a  cylinder or the lift pump for a while raising the oil level and then had a catastrophic failure while pulling out.

 

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You'd expect to blowing lots of blue or even white smoke out the exhaust if there was a serious issue with the bore sealing. Even the best diesels have a fair bit of blow by just because of the high compression they operate at. I'd try eliminating the simple stuff first. But if you do want to check the sealing of the cylinders, a leakdown test is probably the more appropriate test.

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8 minutes ago, Toecutter's Ghost said:

You'd expect to blowing lots of blue or even white smoke out the exhaust if there was a serious issue with the bore sealing. Even the best diesels have a fair bit of blow by just because of the high compression they operate at. I'd try eliminating the simple stuff first. But if you do want to check the sealing of the cylinders, a leakdown test is probably the more appropriate test.

Yup 

and typically problems are simple 

check the obvious first 

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A leak test is more informative than a compression test but requires compressed air so not that simple dockside.

A compression test should be high up on the list.

I didn't seen anything about your exhaust (other than questions about it) - is it smoking? when and what colour? Is it down on power?

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12 minutes ago, SloopJonB said:

A leak test is more informative than a compression test but requires compressed air so not that simple dockside.

A compression test should be high up on the list.

I didn't seen anything about your exhaust (other than questions about it) - is it smoking? when and what colour? Is it down on power?

Ya, compression test a good idea if cheap to do. A really leaky piston may not make smoke: no fire, no smoke. All the fuel blown into crankcase. All speculation though. 
 

Low cost compression check for total failure is to turn the crank (the right direction) by hand. On a 3 cylinder expect serious resistance each 240 degrees. My guess is you will get two compressions then nothing for 480 degrees. If that proves true you save the pointless big mechanic compression test cost. 

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25 minutes ago, SloopJonB said:

A leak test is more informative than a compression test but requires compressed air so not that simple dockside.

A compression test should be high up on the list.

I didn't seen anything about your exhaust (other than questions about it) - is it smoking? when and what colour? Is it down on power?

The exhaust didn't seem excessively smoky.  It always smoked a little bit but I haven't noticed a big difference.  I haven't left the slip so I'm not sure about power.  However, at higher RPM's it sounded normal  before spitting the dipstick.

 I hadn't thought of a leak test.  Could I use a scuba tank?

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17 minutes ago, El Borracho said:

Ya, compression test a good idea if cheap to do. A really leaky piston may not make smoke: no fire, no smoke. All the fuel blown into crankcase. All speculation though. 
 

Low cost compression check for total failure is to turn the crank (the right direction) by hand. On a 3 cylinder expect serious resistance each 240 degrees. My guess is you will get two compressions then nothing for 480 degrees. If that proves true you save the pointless big mechanic compression test cost. 

good idea...I can probably lift two of the three compression levers to test one cylinder at a time making the hand turn easier?

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8 minutes ago, Tharsheblows said:

The exhaust didn't seem excessively smoky.  It always smoked a little bit but I haven't noticed a big difference.  I haven't left the slip so I'm not sure about power.  However, at higher RPM's it sounded normal  before spitting the dipstick.

 I hadn't thought of a leak test.  Could I use a scuba tank?

A good cylinder is its own air pump. Built in 2 MPa (350 psi?) by just turning over the engine.

This subject engine has had a spectacular failure. The cause will be obvious. 

9 minutes ago, Tharsheblows said:

good idea...I can probably lift two of the three compression levers to test one cylinder at a time making the hand turn easier?

Maybe. Usually the engine will leak enough to allow hand turning to pass the compression point slowly.

You could get off easy with just a hugely blown head gasket. Unlikely in your case though. 

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2 minutes ago, El Borracho said:

You could get off easy with just a hugely blown head gasket. Unlikely in your case though.  

I was hoping for this outcome but, I agree, I don't think its likely because there is no water in the oil. 

I wasn't sure if there are any empty holes located adjacent to a cylinder that run straight to the oil pan.  I've never actually seen the stripped block.

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Cranking excessively to bleed fuel system,  water still pumping to fill the water lock muffler, hydraulic lock on at least one cylinder and bent rods with scored bores. Head off for inspection time. 

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6 minutes ago, Crazy Horse said:

Cranking excessively to bleed fuel system,  water still pumping to fill the water lock muffler, hydraulic lock on at least one cylinder and bent rods with scored bores. Head off for inspection time. 

We turned off the through hole for raw water for that purpose...but that might have been the cause from before.

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My vote would normally be a broken ring but spitting the dipstick out with that much force, might be a piston failure. 

A failed head gasket should quickly show up as oil in the coolant. And maybe steam in the exhaust.

If you think the lift pump is leaking diesel then smell the oil on the dipstick. It will smell of diesel. Of course a leaking cylinder might also do this but a leaking lift pump leaks diesel a lot faster into the crankcase. A faulty injector can also cause this but I think this is rarer.

The breather on that engine just goes into a little box with a baffle to slow the flow of oil mist and allow it to condense and be sent back to the intake. Not even steel wool in it. So I don't think blocked breather tube. It's very easy to unscrew the cover with 3 or 4 small bolts and check and also remove the breather hose. But if you're seeing smoke... combustion is happening in a cylinder and getting into the crankcase.

Hard to start? Again, ring or piston has failed so low compression on one cylinder.

I'm really familiar with turning over a 3GM30F by hand. 27mm socket and a 1/2" socket wrench is enough. Don't use the compression release on the other 2 cylinders. You want to feel what each piston feels like as it is coming up to TDC and compressing the air in there. If one feels off you'll soon know.

This is probably just as informative as a compression test.(which requires special adapters to fit in the injector hole; these differ from engine to engine; this is why diesel compression testing is a PIA compared to a spark plug testing on a gas engine)

 

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4 minutes ago, Zonker said:

My vote would normally be a broken ring but spitting the dipstick out with that much force, might be a piston failure. 

A failed head gasket should quickly show up as oil in the coolant. And maybe steam in the exhaust.

If you think the lift pump is leaking diesel then smell the oil on the dipstick. It will smell of diesel. Of course a leaking cylinder might also do this but a leaking lift pump leaks diesel a lot faster into the crankcase. A faulty injector can also cause this but I think this is rarer.

The breather on that engine just goes into a little box with a baffle to slow the flow of oil mist and allow it to condense and be sent back to the intake. Not even steel wool in it. So I don't think blocked breather tube. It's very easy to unscrew the cover with 3 or 4 small bolts and check and also remove the breather hose. But if you're seeing smoke... combustion is happening in a cylinder and getting into the crankcase.

Hard to start? Again, ring or piston has failed so low compression on one cylinder.

I'm really familiar with turning over a 3GM30F by hand. 27mm socket and a 1/2" socket wrench is enough. Don't use the compression release on the other 2 cylinders. You want to feel what each piston feels like as it is coming up to TDC and compressing the air in there. If one feels off you'll soon know.

This is probably just as informative as a compression test.(which requires special adapters to fit in the injector hole; these differ from engine to engine; this is why diesel compression testing is a PIA compared to a spark plug testing on a gas engine)

 

Thank you!  I'm hearing that a manual hand turn is probably all the confirmation of a serious problem that I need before ripping in deeper.  So no need to track down the adapter and get actual numbers.  Its certainly worth a try before I buy more tools.

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I think so. When I got my engine hydro-locked (several times) I would turn if over by hand several times to clear the cylinder(s) of water before trying to start it. 

If the compression releases are open its very easy to turn it by hand but you never feel any resistance from compression. You could however try it both ways.

 

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12 minutes ago, Tharsheblows said:

That’s a great idea.

Sorry, I checked the manual, that engine has a precombustion chamber under the injector, so you can’t see past it with an endoscope...

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7 hours ago, Zonker said:

When I got my engine hydro-locked (several times) I would turn if over by hand several times to clear the cylinder(s) of water before trying to start it. 

Several times?

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Yup. shallow bilges. The water lift muffler was right at min distance Yanmar wanted below the mixing elbow. In really rough seas a small amount of water would manage to move (pitching action) into the aft most cylinder. Didn't happen very often; maybe every 2 years? Probably 4 or 5 times total. 

You'd know instantly because the starter motor would just go "clunk". Didn't bend anything inside as far as I knew; the engine ran the same afterward.

 

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Here is an update on this issue:

 

We performed a hand turn compression test as suggested and found that one piston was difficult (good compression) and the other two were quite easy.  After playing with the compression levers we determined that the cylinder making good compression was cylinder 1 (counting from the end with the belt).  We then performed a compression test with a compression tester and determined that cylinder 1 was making 410 pi and the other two where making about 210 psi.  This confirmed a compression problem.  (note: the compression tester didn't really give us much more information than the simple hand turn.  That's a good trick.)

I suspected: 1) bad rings, 2) some kind of valve issue; or 3) a head gasket issue.

We then removed the head and found relatively clean and nice looking pistons and valves and no obvious signs of a blown head gasket.

Here are my thoughts:

1) We haven't removed the pistons yet so it might still be the rings (is there a way to test the integrity of the rings at this point with the head off?);

2) I would expect a blown head gasket to show visible signs but because two adjacent cylinders had low and relatively equal compression we could have been experiencing a head gasket breach between the cylinders back and forth...that would allow compression to go through the head into the oil pan and blow the dipstick out;

3) while the valves looked really good at a glance we haven't run any test to see how well they are seated;

4) The combustion chamber on cylinder two seem recessed a bit more than 1 and 3....I'm wondering if that is a sign of an issue or what might cause that.  (Ive never dissembled the head so I'm not entirely aware of the structure)

 

Thoughts?

 

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The fact that the neighboring pistons both had roughly half the normal compression is circumstantial evidence of a head gasket breach between them (double the volume, half the pressure) but wouldn't explain the pressurization of the bottom half. When you examine the web between cylinders 2 and 3 on the head and on the block, do you see any carbon streaks or gas scoring?

Regarding the rings, one thing the compression tester can give you that a hand turn can't is some of the leakdown dynamics. How fast the pressure drops from peak after you achieve TDC (and stop turning) can tell you how bad your leakage is. In this case, if cylinders 2 and 3 hold pressure about as well as #1, that would argue that it's not bad rings or valves, but more evidence of communication between the cylinders.

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1 hour ago, IStream said:

The fact that the neighboring pistons both had roughly half the normal compression is circumstantial evidence of a head gasket breach between them (double the volume, half the pressure) but wouldn't explain the pressurization of the bottom half. When you examine the web between cylinders 2 and 3 on the head and on the block, do you see any carbon streaks or gas scoring?

Regarding the rings, one thing the compression tester can give you that a hand turn can't is some of the leakdown dynamics. How fast the pressure drops from peak after you achieve TDC (and stop turning) can tell you how bad your leakage is. In this case, if cylinders 2 and 3 hold pressure about as well as #1, that would argue that it's not bad rings or valves, but more evidence of communication between the cylinders.

The head gasket looked very good.  I guess it could still could have failed without visible signs but I would have thought a failure would be visibly obvious.

Regarding the compression test, I wish I had thought of releasing the pressure from the gauge and watching the leak down rate.  I just looked at the high pressure recorded by the gauge and moved to the next cylinder.  It guess its too late now for this project because the head is already removed.  I learn something new everyday!

Another sign that the problem might be the rings is that we sprayed Triflow on the pistons before covering the block with towel and leaving it for the day just to protect against humidty/water and it looked like the Triflow was very slowly draining out of cylinders 2 and 3 and was not noticeably draining from cylinder 1.

 

Another thought:  The engine is mounted at an angle with the highest end being the first cylinder (the good one) closest to the end with belts which faces toward the stern.  The drive shaft initially exists the transmission toward the bow and then enters a V-drive and changes direction and exists through the hull toward the stern again to the prop.  The reason I say this is because we initially saw that the oil looked over-filled which we suspected was because the lift pump diaphragm was leaking diesel into the oil causing the oil level to rise.  Could over-filled oil apply force to and damage the rings of the "lower cylinders" from below and possible spare the "higher" cylinder?

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2 hours ago, Tharsheblows said:

1) We haven't removed the pistons yet so it might still be the rings (is there a way to test the integrity of the rings at this point with the head off?

Drop them a bit from TDC and put some diesel in the cylinders to see what the drainage is like.

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17 hours ago, Tharsheblows said:

The head gasket looked very good.  I guess it could still could have failed without visible signs but I would have thought a failure would be visibly obvious. 

you need to rule out a cracked head or block between the two bad cylinders.... dye penetrant test is pretty straightforward if a bit messy.

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It appears that half the air from two of three cylinders might be pumping into the crankcase. That is a significant volume. Certainly would explain the original symptoms. A gasket leak between cylinders would not. 

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On 2/10/2021 at 4:54 PM, Tharsheblows said:

Another sign that the problem might be the rings is that we sprayed Triflow on the pistons before covering the block with towel and leaving it for the day just to protect against humidty/water and it looked like the Triflow was very slowly draining out of cylinders 2 and 3 and was not noticeably draining from cylinder 1.

 

  Could over-filled oil apply force to and damage the rings of the "lower cylinders" from below and possible spare the "higher" cylinder?

that is the shade tree mech test for bad rings oil and leaking down

no but diesel in the oil will cause the ring wearing as it reduces the oil viscosity [thinner/weaker oil film = worn rings]

anyway the upper rings are compression lower rings oil control wipers

plastic gauge the rods and main bearings as thin oil will get them also 

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1 hour ago, Blitz said:

Pour some diesel into the intake and exhaust ports and look for leakage past the valves to rule out a problem there.

Leaky valves would not pressurize the crankcase. 

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31 minutes ago, El Borracho said:

Leaky valves would not pressurize the crankcase. 

They could in principle through the vent holes from the head down to the crankcase if the valve cover vent was blocked but that's not what's happening here.

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54 minutes ago, IStream said:

They could in principle through the vent holes from the head down to the crankcase if the valve cover vent was blocked but that's not what's happening here.

That would be the valve stems leaking. Doubt that tiny flow could ever launch a dipstick. 

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9 hours ago, Zonker said:

A failed head gasket USUALLY looks bad.

But the way you described the failure "sneezed and died" doesn't sound like rings i.e. just 1 cylinder failing...

We discussed the possibility that we were running with a bad cylinder for some time and then the "incident" is when we lost a second cylinder.  Based on just my description do you suspect the head gasket?  or a crack in the head that doesn't involve water?

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16 hours ago, Blitz said:

Pour some diesel into the intake and exhaust ports and look for leakage past the valves to rule out a problem there.

If the valves have tiny amounts of carbon on them, they will slowly leak anyway (like over a few minutes). So not an exact test.

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2 hours ago, Blitz said:

True, but it gives you an idea.  While the head is off I would disassemble inspect and lap all the valves.  It's not a big job to do it.

Yes, now that the engine is apart we plan on changing all reasonably inexpensive parts and giving everything proper attention.  I just wish the problem was "obvious." 

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2 hours ago, Tharsheblows said:

Yes, now that the engine is apart we plan on changing all reasonably inexpensive parts and giving everything proper attention.  I just wish the problem was "obvious." 

I thought the compression test made the problem obvious. Especially given the excessive blow-by symptom. 
 

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I'm not going to re-read the thread to see if it has been mentioned but how about the PCV system?

Is it clear? They used to be a huge PITA on the early controlled car engines.

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Just now, El Borracho said:

I thought the compression test made the problem obvious. Especially given the excessive blow-by symptom. 
 

Yes, the compression test confirmed that there is a compression problem in the second and third cylinders.  I strongly  believe the rings are most likely a problem but that is still not 100% definite because the cylinder wall look so good.  Also, I still have not taken the pistons out and looked at the rings.

What I mean by "obvious" is that in the past when I took apart an engine I saw something that looked "obviously" bad immediately.

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19 minutes ago, SloopJonB said:

I'm not going to re-read the thread to see if it has been mentioned but how about the PCV system?

Is it clear? They used to be a huge PITA on the early controlled car engines.

The Yanmar 30GM3F has a breather that comprises a little box on the valve cover that has an internal splash guard and an external hose connected back to the air inlet.  That hose initially popped off and sprayed the engine with oil  (probably due to overfill and pressure).  I confirmed that it isn't blocked but when we ran the engine with the hose disconnected it blew a steady stream of white smoke...(Not good)

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17 minutes ago, El Borracho said:

I thought the compression test made the problem obvious. Especially given the excessive blow-by symptom. 
 

And yes, the white smoke in the crank case and no water in the oil makes a blown head gasket less likely (I think) and a head issue probably less likely (seems like the smoke would have to blow all the way past the valve stem to get to the crank case?)

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Excessive blow-by does not require damaged or worn cylinder walls. Common for ring failure to be at the piston surfaces. Air passes inside the rings because scoring or carbon between the ring and piston. Especially if the ring was sticking and banging up and down against the soft aluminum because of the poor lube. Might not be readily apparent to someone not used to looking at pistons. Also a bit of a chore to remove the pistons. If the engine bearings are not ‘end of life’ one can replace pistons and rings and get some more hours from an engine. That would seem unlikely in your case however...considering the age and that the engine was run on diesel lube. Might get a year or two of casual use, though.

Valve stem leakage is not much of an issue in non-turbo diesels because the low pressure differences....no vacuum. Plus the clearance would need to be huge. 

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I can't imagine getting to the point of pulling pistons/rods and not doing the crank - at least polishing the journals and putting in new bearings.

I mean WTF - if the rods & pistons are out why would you stop there?

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35 minutes ago, SloopJonB said:

I can't imagine getting to the point of pulling pistons/rods and not doing the crank - at least polishing the journals and putting in new bearings.

I mean WTF - if the rods & pistons are out why would you stop there?

Because the project goes from a few hours and dollars to a full rebuild. Depends on the sailors situation. When I was broke-ass I serviced just one of four pistons. Ran great for many sea miles until the next weak link exposed itself. But the El Borracho is a DIY tinkerer and minimalist. Today, as an internet bazillionaire, I would just pop a new engine in and not think about why it broke. 
The instant engine would run okay as a one cylinder. So that is a shade tree option too. Heh. 

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On 2/4/2021 at 10:57 AM, Tharsheblows said:

I have a Yanmar 30GM3F that is spitting the dipstick out like a rocket.  I obviously have some unwanted compression in the oil pan.  Its about 30 years old so it wouldn't surprise me if it needs new rings but I thought I would run it by anyone who wants to help me diagnose the issue.  Here is what happened so far.

 

1) it was very difficult to start so we bleed all the lines repeatedly and eventually got it started but then after a few minutes it blew the dipstick;

2) I read somewhere that a blocked breather could cause unwanted pressure in the oil so I pulled the hose off the breather and saw that smoky air was blowing out pretty freely so I decided it probably wasn't blocked...but I'm not sure if "smoky air" should even be blowing out of the breather.

3) We checked the oil and saw that it was unusually high.  We could have overfilled it but I assumed that the lift pump diaphragm might have been busted and slowly leaking diesel into the oil eventually raising its level so we changed the oil and replaced the lift pump.  (after bleeding it forever, again, we got it started started and then it blew out the dipstick again)

4) At this point I'm pretty sure I'm getting compression in the oil so I narrowed the problem to these guesses:

         1) bad rings;

         2) a weird head gasket failure that isn't introducing water to the oil but somehow is introducing compression to the oil through one of the holes in the block (not sure if that is even           

              possible); or

         3) a hole in a piston.

My next action is to check the compression in each cylinder to get that data point before tearing it apart.

Any thoughts? Suggestions?

 

 

you have a blocked cranckcase vent and whats popping the dipstick is the bypass from the oil pump building pressure in the crankcase, as a rule most yanmars (leastways my 2QM20) which have a combined dipstick tube and oil drain will also give you the most rapid oil change out into the bilges you'll ever see

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6 hours ago, Blue Crab said:

So it's not all bad?

hopefully not , but if you think about it the dipstick is the path of least resistance, any probs running with oil filler cap removed ?

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On 2/14/2021 at 11:37 AM, 167149 said:

hopefully not , but if you think about it the dipstick is the path of least resistance, any probs running with oil filler cap removed ?

I never ran it with the oil filler cap removed but I did check the breather which was clear and then ran it with the breather tube disconnected and it blew a steady stream of white smoke.

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A few follow-up questions:

1) What should a full rebuild cost (in southern California) assuming I have to bore out the cylinders the minimum amount and buy new pistons and replace all parts that one would once they are that deep in the engine? (yanmar 30GM3F)

2) What do you think a comparable new engine would cost...including other things that I might have to buy as well like a new v-drive maybe?

and the most important question:

3) How close to the cost of a new engine would you pay before its crazy to not just buy a new one?

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DIY remove and replace? Or risking huge cost uncertainties with a mechanic? Given that the engine and transmission are old and of uncertain condition I would buy new and be done with it. The new engine and transmission cost vs. rebuild can start to look small compared to labor.  But financial situations vary so anything is reasonable. 

No reason to restrict rebuilds to So Cal. Much engine work is done in the midwest. There is nothing particularly special about that engine, either, so no need for marine or Yanmar branding of the shop.

Back in #1 you said the age is 30 years.  Every component is a candidate for renewal at that age. Hoses, wires, instruments, controls, tank, heat exchanger, shaft & seal, even the engine room paint and soundproofing. Etc.

Have you yet determined the cause? That little engine should have been on the garage bench by now for a good looky-loo. Might be something simple.

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A new Beta 30 runs around $10k with gearbox, panel, etc, and should fit on the existing beds with minimal mods. Equivalent Yanmar and Volvo will be similar price.

I would expect a rebuild to be in the 5-7k range, and that's not including external stuff like alternator, water pump, gearbox, etc. Might get it done cheaper elsewhere or DIY but still a good chunk of the new engine cost.

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17 hours ago, El Borracho said:

DIY remove and replace? Or risking huge cost uncertainties with a mechanic? Given that the engine and transmission are old and of uncertain condition I would buy new and be done with it. The new engine and transmission cost vs. rebuild can start to look small compared to labor.  But financial situations vary so anything is reasonable. 

No reason to restrict rebuilds to So Cal. Much engine work is done in the midwest. There is nothing particularly special about that engine, either, so no need for marine or Yanmar branding of the shop.

Back in #1 you said the age is 30 years.  Every component is a candidate for renewal at that age. Hoses, wires, instruments, controls, tank, heat exchanger, shaft & seal, even the engine room paint and soundproofing. Etc.

Have you yet determined the cause? That little engine should have been on the garage bench by now for a good looky-loo. Might be something simple.

We pulled it out and had a guy looking at it.  He said that all three cylinders show scoring on the cylinder walls.  He suggested boring .25mm and all new parts.  He quoted 5k in labor plus parts.  I'm assuming about 8.5 k total.  I'm just thinking that if I can really get a new engine for 10K that essential drops in without too much redesign then that is what I should do.

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5K to refresh a small diesel sounds like a "marine" price.

Take it to a regular engine shop.

Changing engines will cost you probably 50% more than the engine price. All the bits & pieces really add up.

My first engine swap was a "like for like" swap of a Yanmar single - I put in a new on the pallet YSM 8 to replace a cooked YSE 8 - same engine, just a Mark II sort of thing.

I did everything myself and it still cost 25% over the price on the pallet.

Changing to a different engine will bump that up substantially, even if they claim it's a "drop in" replacement.

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I saw you mentioned a v-drive - that might complicate things a bit.

Other than that, I'd call around and get some pricing on a new engine, and take some measurements. Beyond the basic mount spacing and "will it fit", consider things like exhaust size and routing (Beta and modern Yanmars are opposite to the 3GM), control cable routing, panel size (extra hassle if you need to modify your panel mount). Beta calls for a 3" blower hose which can be a hassle to install - not sure if Yanmar calls for that. But given $8.5k for a rebuild, I would be seriously looking at a new engine as a better long term solution.

For reference, in 2019 I paid the equivalent of $8k USD for a Beta 25 w/ an upgraded panel and alternator. On top of that I had about $3k in installation costs (DIY), for prop shaft inspection/cleanup, new PSS shaft seal, new Racor, fuel hoses, blower + vent hose, raw water hose, strainer, anti-syphon loop, and sound insulation.

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On 2/4/2021 at 9:41 AM, Tharsheblows said:

I think combustion blow-by would certainly pressurize the oil and blow the dipstick out.  The fact that the engine has a breather means (I assume) some blow by is expected and normal? no?

Does anyone know the classic signs of failing rings?  I'm guessing failure to start immediately might be a sign (low compression).

First check and adjust valve clearances. Often rocker/head pressurisation can be caused by incorrect valve clearance causing backpressure in the rocker and blowout either the dipstick or head breather.. If the engine runs without excess smoke, chances are the rings are ok. But a compression test kit(cheap one will do) on each bore will confirm. Good luck. 

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On 2/16/2021 at 8:21 PM, Tharsheblows said:

I never ran it with the oil filler cap removed but I did check the breather which was clear and then ran it with the breather tube disconnected and it blew a steady stream of white smoke.

Yup, rings or bore or head to crank timing.. 

 

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1 hour ago, FixinGit said:

First check and adjust valve clearances. Often rocker/head pressurisation can be caused by incorrect valve clearance causing backpressure in the rocker and blowout either the dipstick or head breather.. If the engine runs without excess smoke, chances are the rings are ok. But a compression test kit(cheap one will do) on each bore will confirm. Good luck. 

Well..this thread is well past this...#66...but your post makes no sense. Bad valves cannot cause blow-by into the rocker or anywhere else because both intake and exhaust manifolds are open to the atmosphere...not connected to the crankcase in any way. And the path to the rocker cover is via the valve stems which if you understand how air pumps work are in no position to pump any air...being outside the cylinder.

Bad valve seats or timing reduce blow-by. 

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1 hour ago, El Borracho said:

Well..this thread is well past this...#66...but your post makes no sense. Bad valves cannot cause blow-by into the rocker or anywhere else because both intake and exhaust manifolds are open to the atmosphere...not connected to the crankcase in any way. And the path to the rocker cover is via the valve stems which if you understand how air pumps work are in no position to pump any air...being outside the cylinder.

Bad valve seats or timing reduce blow-by. 

Uh huh...... valve adjustment /timing CAN lead blow back. Gases are blown back past the valve on compression stroke of the piston..

White smoke emanating from the rocker is a sure sign of valve leakage or breather/sump pressure. 

But you are correct that the thread is beyond my comments now but i appreciate your trying to educate me...Thanks.

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20 minutes ago, FixinGit said:

Uh huh...... valve adjustment /timing CAN lead blow back. Gases are blown back past the valve on compression stroke of the piston...

...out the intake manifold into the atmosphere. Not into the rockers or crankcase. At least on this planet. :)

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2 minutes ago, El Borracho said:

...out the intake manifold into the atmosphere. Not into the rockers or crankcase. At least on this planet. :)

Haha.. :)

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I have re read my previous posts to try and understand where i went wrong trying to convey my thoughts... Not only was my post timing a mile out but i can only put my inability to understandably express my thoughts down to a head injury.. Had taken a few months break from SA for the same reason. 
I seem to have my motor running but wrong gear selected or perhaps worn rings or bore myself.. 

Whatever the heck you decide Tharsheblows, i have the Beta in mine currently and cant fault it for agricultural simplicity and cheaper parts than the yanmar. My apologies for hijacking your thread. 
Good luck. 

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On 2/23/2021 at 11:51 AM, Tharsheblows said:

We pulled it out and had a guy looking at it.  He said that all three cylinders show scoring on the cylinder walls.  He suggested boring .25mm and all new parts.  He quoted 5k in labor plus parts.  I'm assuming about 8.5 k total.  I'm just thinking that if I can really get a new engine for 10K that essential drops in without too much redesign then that is what I should do.

You need to understand what caused the scoring in all 3 bores, most likely a partial seizure from overheating or least likely bent con rods thrusting the pistons on that side. Other options could be corrosion in the bore from water sitting or dirt/foreign object ingress.

Oil pump bypass will not cause high crank case pressure, I am always open to new ideas but that ones is off the scale.

The crank case is designed to cope with the rapid movement of air from pistons moving up and down, windage from crank, con rods etc, compression slipping past the rings and oil being thrashed around.

Your engine can’t cope with the increase in blow by so found the weakest link which is the dipstick in your case. Chances are many external seals would have been stressed to the point of leaking.

If the cylinders do infact need a rebore and the cost of Yanmar parts a new engine may be a better investment. You could do the rebuild yourself with the machining done by an engine reconditioner but you need to do a thorough job to not repeat the issue.

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